When the reset signal is de-asserted, the HW-controlled bootstrap starts running unless it is disabled in the SoC integration. It issues some commands to detect a NAND chip, and sets up registers automatically. Until this process finishes, software should avoid any register access.
Without this delay function, some of UniPhier boards hangs up while executing nand_scan_ident(). (denali_read_byte() is blocked)
Signed-off-by: Masahiro Yamada yamada.masahiro@socionext.com ---
Changes in v2: None
drivers/mtd/nand/raw/denali_dt.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/mtd/nand/raw/denali_dt.c b/drivers/mtd/nand/raw/denali_dt.c index 91d0f20aae..1afc61f876 100644 --- a/drivers/mtd/nand/raw/denali_dt.c +++ b/drivers/mtd/nand/raw/denali_dt.c @@ -136,11 +136,19 @@ static int denali_dt_probe(struct udevice *dev) }
ret = reset_get_bulk(dev, &resets); - if (ret) + if (ret) { dev_warn(dev, "Can't get reset: %d\n", ret); - else + } else { reset_deassert_bulk(&resets);
+ /* + * When the reset is deasserted, the initialization sequence is + * kicked (bootstrap process). The driver must wait until it is + * finished. Otherwise, it will result in unpredictable behavior. + */ + udelay(200); + } + return denali_init(denali); }